//HashMap/HashSet in c Sharp
HashSet<int> numbers = new HashSet<int>();
// below are the methods
numbers.Add(2);
numbers.Remove(2);
//Removes all elements that match the conditions
//defined by the specified predicate from a HashSet<T> collection.
numbers.RemoveWhere(Predicate<T>);
//Removes all elements from a HashSet<T> object.
numbers.Clear();
// Determines whether a HashSet<T> object contains the specified element
numbers.Contains(0);
// The collection of items to remove from the HashSet<T> object.
numbers.ExceptWith(anotherHashset);
// Modifies the current HashSet<T> object to contain only
// elements that are present in that object and in the specified collection.
numbers.IntersectWith(IEnumerable<T>);
// Searches the set for a given value and
//returns the equal value it finds, if any.
numbers.TryGetValue(T, T)
numbers.UnionWith(IEnumerable<T>) //